"It's a very serious issue. We have already filed a written complaint to the state Election Commission about the EVM tampering. We will now take up the issue at the national level," Gogoi stated.

The Election Commission on Wednesday had conducted trial polling in Jorhat where the light on the EVM against the BJP symbol was blinking irrespective of other buttons being pressed.

Assam Chief Election Officer Vijayendra, however, said it was not a case of tampering. "It was not a case of tampering at all. That particular machine was a defective piece. We have changed it," he said.

"The other EVMs across the state will also be checked as per standard procedure in the presence of representatives of all political parties," Vijayendra said.

With 4.5 lakh first time voters, Assam will see an electorate of 1.87 crore exercising their franchise during the Lok Sabha elections in three phase on April 7, 12 and 24.